#include<bits/stdc++.h>
#define ll long long
#define vi vector<int>
#define vll vector<ll>
#define eb emplace_back
#define pb push_back
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
#define sz(v) ((int)v.size())
#define pii pair<int,int>
#define pll pair<ll,ll>
#define fi first
#define se second
#define umap unordered_map
#define uset unordered_set
#define mset multiset
#define ui unsigned int
#define ull unsigned ll
#define i128 __int128
using namespace std;

namespace qiqi {
	void fail() {
		cout << "Impossible\n";
		return;
	}
	void main() {
		int n,m; string s;
		cin >> n >> m >> s;
		vi mn(n+1),mx(n+1),nxt(n);
		auto cr = [&](const string &s,int i,int j) {
			if (j == n) {
				return pair(0,j-i-1);
			}
			else {
				int len = j-i;
				if (s[i] != s[j]) {
					return pair(1,len+len%2-1);
				}
				else {
					return pair(0,len-len%2);
				}
			}
		};
		for (int i = n-1,lst = n; i >= 0; i--) {
			nxt[i] = lst;
			if (s[i] != '?') {
				auto [pmn,pmx] = cr(s,i,lst);
				mn[i] = mn[lst]+pmn;
				mx[i] = mx[lst]+pmx;
				lst = i;
			}
		}
		auto calc = [&](string s) {
			int c = 0;
			for (int i = 1; i < n; i++) {
				if (s[i] != '?') {
					c += s[i] != s[i-1];
				}
				else {
					int p = nxt[i];
					bool flg = 0;
					for (char ch = '0'; ch < '1'+1; ch++) {
						s[i] = ch;
						int nc = c+(ch != s[i-1]);
						auto [pmn,pmx] = cr(s,i,p);
						if (nc+pmn+mn[p] <= m && nc+pmx+mx[p] >= m) {
							flg = 1; c = nc; break;
						}
					}
					if (!flg) {
						return string();
					}
				}
			}
			if (c == m) {
				return s;
			}
			return string();
		};
		if (s[0] != '?') {
			auto t = calc(s);
			if (!t.empty()) {
				cout << t << '\n';
				return;
			}
			return fail();
		}
		else {
			s[0] = '0';
			auto t = calc(s);
			if (!t.empty()) {
				cout << t << '\n';
				return;
			}
			s[0] = '1';
			t = calc(s);
			if (!t.empty()) {
				cout << t << '\n';
				return;
			}
			return fail();
		}
	}
}

int main() {
//	clock_t st = clock();
//	freopen("test.in","r",stdin);
//	freopen("test.out","w",stdout);
	ios::sync_with_stdio(false);
	cin.tie(nullptr);

	int T = 1;
	cin >> T;
	while (T--) {
		qiqi::main();
	}

//	cout << (double)(clock()-st)/CLOCKS_PER_SEC;
	return 0;
}